1. Field of the Invention
The present invention relates to an improved seal for portions of electrical conductor cables from an external power source, that are connected in a confined location in hazardous locations to corresponding conductor cables for electrical equipment such as submersible pumps in underground wells, instrumentation, heaters, or any other suitable electrical equipment, both underground and above ground. Such seals are used to prevent gas and other combustible fluids from migrating from the electrical equipment into the conductor cable.
The invention is particularly useful for shielded electrical cable used in hazardous electrical locations, where the cable must be sealed on order to prevent migration of gas or other combustible fluids into the cables, conduits or raceways to a non-hazardous location, in order to comply with the requirements of the National Electric Code's Hazardous Section 501.5(f)(3), for Class 1, Div. 1 and Div. 2 hazardous locations.
2. Background of the Invention
In installations in which electrical equipment is used in hazardous locations, such as for example underground wells and refineries, electrical power is supplied from an external source to electrical equipment through insulated conductors that extend into a confined location such as a closed housing where the conductor cable is spliced or otherwise connected to conductor cable that runs to the equipment. This confined area forms a closed transition zone for the cables and house their connections. The portions of the cable conductor from the external power source must be sealed in order to block gases and other combustible fluids that emanate from the equipment, from flowing to the external power source along the conductor cables and cause an explosion.
The housing that confines the connections and seals are located in a hazardous location called a “classified” location. Such locations are referred to as “classified” because they are defined or classified by industry standards such those promulgated by the American Petroleum Institute. The equipment and facilities for such classified locations must be in compliance with the Occupational Safety and Health Act (“OSHA”) Section 1910, Subpart S, for locations where hazardous concentrations of gases or vapors are present because of leakage.
Recent changes to the National Electric Code (“NEC”) require that all medium voltage (“MV”) cable (C-L-X Type MC-HL cables) used in Classes I, II and III, Division 1 and 2, and Class I, Zone 1 and 2 hazardous locations (NEC Articles 501, 502 and 503), must be shielded with a conductive material along its length. This change resulted in the use of a thin layer of uncoated copper tape wrapped around the length of each of the conductors that supplies electrical power to electrical equipment from an external power source.
However, the NEC changes did not address the problem of how to seal the shielded conductor in a confined location in order to prevent gases and other hazardous fluids from migrating along the conductor cable and into the power source and cause an explosion.
Thus, there is need for seal for a shielded conductor cable within such a confined location in order to eliminate a hazardous condition by preventing combustible gas and other fluids that emanate from electrical equipment and flow into the confined location, from migrating along the conductor cable to an electrical power source located outside the confined location.